In general, a parking brake apparatus is used to prevent a parked vehicle from moving.
The parking brake apparatus is classified into a manual parking brake apparatus that the user manipulates by hand, and an electronic parking brake apparatus that is operated by a motor, and the electronic parking brake (EPB) apparatus brakes wheels while converting rotational motion of the motor into rectilinear motion.
That is, in the case of the electronic parking brake apparatus, when the user operates the motor by manipulating a button, a switch, or a lever, a gear unit and a nut screw are rotated as the motor is rotated, a bolt screw, which penetrates the nut screw, is moved in a longitudinal direction thereof, and a parking cable connected to the bolt screw is pulled such that a brake friction member and a brake drum come into close contact with each other, thereby braking a vehicle by using parking braking force that is generated when the brake friction member and the brake drum come into close contact with each other.
In the related art, in order to park the vehicle, the user manipulates the parking brake apparatus to park the vehicle after the user operates a main brake first. When the user releases the main brake after the user manipulates the parking brake apparatus in a state in which the main brake has been operated, parking braking force of the parking brake apparatus is partially lost such that braking force may be decreased during a braking operation, or frictional force between the brake friction member and the drum of the wheel is decreased due to contraction of the brake friction member caused by a change in temperature, such that parking braking force may be decreased. The decrease in parking braking force causes a parked state of the vehicle to be unstable, and causes the parked vehicle to be undesirably moved, and as a result, there is concern that a safety accident will occur. Accordingly, there is a need for an apparatus that may appropriately prevent a loss of parking braking force.